Thanks Stano, I am still debugging this driver. But I find very strange that sometimes printk() in interrupt handler do not output anything. This makes me very difficult to debug. Is it RT patch's expected behaviour? Or I am doing something wrong?? Jackky -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html